This invention relates to a sensor which uses an optical fiber for monitoring relative movements such as physiological activity, vibrations or movement of structures and apparatus where a strain gauge or displacement monitor would otherwise be used.
Strain gauges are usually used to monitor warning or destructive movements of various structures, such as pipelines, bridges, buildings, etc., or to monitor earth movements. Myoelectric potential detecting devices are sometimes used for physiological sensing, e.g. for monitoring heart beat or other muscle movements. The presence of breathing has been monitored using sound or air pressure sensors attached to the nostrils. Such physiological sensors require electrical connection to the skin, or are otherwise uncomfortable or painful to the patient.
The present invention is a transducer for monitoring vital signs of persons, animals, etc. using a comfortable to use structure. The invention can be adapted to detect non-physiological displacements, such as the movement of buildings, structures, etc. including machinery, bridges, earthquakes, blasts, for security and intrusion alarms, etc., e.g. wherever a strain gauge or displacement transducer can be used.
The present invention uses an optical fiber in a particular form as a strain sensor using the phenomenon of microbending, as will be described below: